The name of the slang language Nadsat comes from Russian. So do many words in the language itself. In Russian, numbers between ten and twenty end with -nadsat. This is like the way the same numbers end with -teen in English. So Nadsat means 'teen'.

Although there is 1950s Russian slang in Nadsat, there are other languages too. However, most words in Nadsat are English or variations of English. One type of English variation used is rhyming slang.